There are some kinds of the non-aqueous electrolyte secondary battery using a metallic battery case. There are the following three typical shapes. The first shape is a shape in which a positive electrode terminal (hereinafter simply referred to a positive terminal) and a negative electrode terminal (hereinafter referred to as a negative terminal) are both insulated from a metallic case. The second shape is a shape in which the negative terminal is insulated from the metallic case serving as the positive terminal. The third shape is a shape in which the positive terminal is insulated from the metallic case serving as the negative terminal.
The non-aqueous electrolyte secondary battery having the shape in which the positive terminal and the negative terminal are both insulated from the metallic case is disclosed in JP-A-2002-164038. A conventional structure example of this shape is shown in FIGS. 5 and 6. In FIGS. 5 and 6, reference numeral 1 denotes a generating element; 2 a metallic case; 3 a cover plate; 4 a positive terminal; 5 a negative terminal; 6 an insulating cylinder; 7 a terminal supporting plate; 8 an aluminum brazing alloy; and 9 a metallic brazing alloy.
This non-aqueous electrolyte secondary battery is manufactured as follows. The generating element 1 of a elliptic cylindrical winding type is housed in a metallic case 2 having a shape of a elliptic cylindrical case. With the cover plate 3 having an elliptical shape being fit in an upper end opening of the metallic case 2, a fitting area is sealing-fixed by welding.
The terminal supporting plates 7 are attached, respectively to both of the electrode terminal 4 connected to the positive electrode of the generating element 1 and the negative terminal 5 connected to the negative electrode of the generating element 1 through the insulating cylinder 6 made of ceramic. Namely, as seen from FIG. 6, the positive terminal 4 is inserted into a through-hole inside the insulating cylinder 6 made of ceramic. This fitting area is sealing-fixed by brazing using the aluminum brazing alloy 8. Further, the insulating cylinder 6 is inserted in an opening slot of the terminal supporting plate 7. The fitting area is sealing-fixed by brazing using the metallic brazing alloy 9. Now, the positive terminal 4 is made of an aluminum alloy because it is not dissolved in a non-aqueous electrolyte solution at a positive electrode potential. The brazing member between the positive terminal 4 and the insulating cylinder 6, which is at the positive electrode potential, is also made of the aluminum brazing alloy 8. The terminal supporting plates 7 are insulated from the positive electrode and the negative electrode so that they are not placed at both the potential of the positive electrode and the potential of the negative electrode. For this reason, the terminal supporting plate 7 is made of an aluminum alloy, stainless steel or nickel-plated iron plate. Where the terminal supporting plate 7 is made of the aluminum alloy, the metallic brazing alloy 9 between itself and the insulating cylinder 6 is made of the aluminum brazing alloy.
The negative terminal 5 shown in FIG. 5, like the positive terminal 4, is also inserted in the through-hole inside the insulating cylinder 6 of ceramic. The fitting area is sealing-fixed by brazing using the copper-alloy brazing such as gold-copper brazing alloy. Further, the insulating cylinder 6 is inserted in an opening slot of the terminal supporting plate 7. The fitting area is sealing-fixed by brazing. Now, the negative terminal 5 is made of copper or copper alloy which is difficult to generate electro-chemical corrosion such as alloying with lithium at the negative electrode potential. The brazing member between the negative terminal 5 and insulating cylinder 6, which is at the negative electrode potential, is made of the copper-alloy system metallic brazing. Further, the brazing member of the fitting area between the terminal supporting plate 7 and insulating cylinder 6 is made of the aluminum brazing alloy as in the case of the positive electrode.
The terminal supporting plates 7, 7 with the positive terminal 4 and negative terminal 5 sealing-fixed through the insulating cylinders 6, 6, respectively are sealing-fixed by welding in a state where they are fit in the opening slots made in the cover plate 3. The generating element 1 attached to the bottom of the cover plate 3 is inserted in the interior of the metallic case 2. Thereafter, with the cover plate 3 fit in the opening at the upper end of the metallic case 2, the interior of the battery case is sealed by welding.
The non-aqueous secondary battery having the shape in which the metallic case serves as the positive terminal and the negative terminal is insulated from the metallic case is disclosed in JP-A-2003-157832. In the battery having this shape, the battery case is made of aluminum. An aluminum foil serving as a positive electrode collector and the battery case are connected through electron conduction by contact or welding. On the other hand, an insulator is provided between the negative terminal and battery case so that the negative terminal is insulated from the metallic case.
Further, the non-aqueous electrolyte secondary battery having the shape in which the metallic case serves as the negative terminal and the positive terminal is insulated from the metallic case is disclosed in JP-A-11-111339. In the battery having this shape, the battery case is made of nickel-plated iron (steel) or stainless steel. A copper foil serving as a negative electrode collector and the battery case are connected through electron conduction by contact or welding. On the other hand, an insulator is provided between the positive terminal and battery case so that the positive terminal is insulated from the metallic case.
Further, JP-A-2001-283926 discloses the following lithium secondary battery. The battery case is made of SUS304; the positive terminal is made of an aluminum alloy; and the negative terminal is made of a copper alloy. The positive terminal and negative terminal are attached to the battery case so that they are insulated therefrom. The positive terminal and battery case are connected to both ends of a bimetal serving as a temperature switch, respectively. Since the temperature switch is normally opened, the positive terminal is insulated from the battery case. However, where the battery has abnormally generated heat because of e.g. overcharge, the temperature switch is closed so that conduction between the positive terminal and battery case is assured. Further, a resistor is provided at a position separated from the lithium battery case, and both ends of the resistor element are connected to the negative terminal and battery case, respectively. The gist of the invention disclosed in this patent document is as follows. When the battery has abnormally generated heat because of e.g. overcharge, the temperature switch is closed so that the positive terminal and negative terminal are connected to each other through the resistor. Therefore, a safety mechanism that the energy accumulated in the generating element is consumed through Joule heating operates. Further, since the resistor generating the Joule heating is provided outside the battery, the battery is excellent in heat dissipation. Claim 2 of this patent document defines that the resistance of the conduction circuit between the positive terminal and negative terminal when the temperature switch is closed is set at Ec/(I0×10) or lower. In this case, Ec represents a charging ending voltage which is managed during normal charging; and I0 represents a current value when the rated capacity of the battery is charged for one hour at a constant current. Further, claim 4 of this patent document discloses that the rated capacity of the lithium secondary battery is set in a range of 1 Ah to 10 Ah.
JP-A-2000-353502 provides the following description. The battery case constructed of an aluminum laminate sheet has been proposed and put into practice. However, the inner resin of the aluminum laminate sheet may be passed through owing to any abnormality such as burr of the electrode collector or mixing of a metallic alien substance into the interior of the battery. In this case, the aluminum foil within the aluminum laminate sheet may be brought into contact with the negative electrode so that it falls into a negative electrode potential. In this case, a lithium-aluminum alloy is created so that the aluminum foil is pulverized. As a result, the airtight of the aluminum laminate deteriorates, thus leading to reduction of reliability of the battery. However, even where the contact occurs between the aluminum foil and the negative electrode, this could not be immediately detected. This problem can be solved by electrically connecting the metal of the laminate sheet to the positive electrode. Such a configuration permits the potential of the laminated metal to accord with the potential of the positive electrode. Thus, where the laminated metal is brought into contact with the negative electrode, this will be detected as a change in the terminal voltage of the battery. As an example of the metal constituting the laminate of the metal and resin, aluminum or its alloy is named. As an example of the method for connecting the metal of the laminated sheet to the positive electrode, connecting the metal of the laminated sheet to the positive terminal by a conductive adhesive tape is proposed. In the battery described in the embodiment disclosed in JP-A-2000-353502, lithium-cobalt composite oxide is employed as the positive electrode active material and graphite is employed as the negative electrode active material.